XTINA, definitely. A lot of the younger gorls (at least on reality singing shows) all have touch of those vocal melismas that she does. It's distinctive. She's collaborated with a ton of legendary icons and artists and her hits back in the day are undeniable.
P!nk has a ton of hits and sells well, but I just can't help but think that she is typically forgotten until she releases new music.
P!nk definitely. Her career from the beginning has been impactful. All of her music videos are creative, artistic, and in most of them hilarious or beautiful. She's pretty heartfelt, and she's a badass who doesn't give a **** what people think, in addition to the fact that she isn't afraid to say that Christina is a bitch.
Beautiful and ****in' Perfect peaked at the same position of the Hot 100, so of course, they're impact is pretty equal in those terms. XTina was impactful until 2008, because she ultimately became a GaGa wannabe.